Roadway markers are utilized in a variety of traffic control applications. Many roadway markers are permanently affixed to a roadway to delineate lanes of traffic on the roadway. Other roadway markers are used to temporarily delineate construction or work areas. Roadway markers used in such applications are called temporary roadway markers. Both permanent and temporary roadway markers are attached to a roadway with a suitable adhesive.
Permanent roadway markers have a low profile and remain in place to define traffic lanes, identify obstacles and perform other well-known functions. While having a low profile, many permanent roadway markers are raised to create a rumble sound in an automobile when the tires of the automobile impact a row of markers. The most commonly used permanent roadway marker is formed of ceramic and has a partially hemispherical, button-like shape. In recent years, alternative roadway markers having inclined surfaces covered with a retroreflective medium in the form of a surface tape or embedded prisms have been developed for use as permanent roadway markers.
Temporary roadway markers serve to notify motorists that a construction area is near and that caution is needed. They often direct roadway traffic to pass along the portions of the roadway unaffected by construction, while protecting workers within a construction area from roadway traffic. After construction is completed, temporary roadway markers are loosened and removed. To be effective temporary roadway markers must alert traffic of the construction area. Typically, temporary roadway markers warn oncoming motorists by the use of visual cues, such as reflective surfaces. Some temporary roadway markers also use physical cues such as causing a vehicle to create a rumbling noise on contact with a marker.
As noted above, both permanent and temporary roadway markers that provide visual cues often have a reflective surface that reflects light back to a driver. Physical cues are provided by a raised portion that causes the automobile to rumble upon contact with the marker. One example of a roadway marker that provides both visual and physical cues is described in U.S. Pat. No. 4,428,320, issued to Oplt et al. and entitled "Reflective Paving Marker." The Oplt et al. patent describes a roadway marker having a generally trapezoidal prism shape with a honeycombed interior, a reflective surface and raised areas. The honeycombed interior makes the marker lightweight, which is desirable. Although the roadway marker is lightweight, one disadvantage of the Oplt et al. roadway marker is its high manufacturing cost. Due to its construction, the Oplt et al. roadway marker must be injection molded. Injection molding is expensive when compared to other manufacturing processes such as extrusion. Many prior art roadway markers share these same disadvantages because they can only be formed by injection or some other molding processes.
In order to overcome the costs disadvantage associated with injection molding, roadway markers having a constant cross-sectional shape along their longitudinal axis have been developed. The constant cross-sectional shape allows such roadway markers to be made by an inexpensive extrusion manufacturing process. Such roadway markers are described in parent U.S. patent applications Ser. Nos. 07/735,321 and 07/694,873 more fully referenced above, the subject matter of which applications is incorporated herein by reference.
In addition to their constant cross-sectional shape, roadway markers of the type described in the foregoing patent applications include a base area suitable for adhesive attachment to a roadway surface, as well as a raised rumble portion. The base area of the marker is relatively large and includes a plurality of adjacent, parallel grooves of arcuate cross section. The arcuate grooves increase the adhesive surface of the marker. The longitudinal lower edges of the base curve downwardly to assist in gripping the roadway surface. The top of the raised rumble portion is scalloped to reduce the weight of the roadway marker. The longitudinal lateral sides of the raised rumble portion of the roadway marker include a recess for receiving a strip of reflective tape. The two orthogonal sides are sheared straight, or inclined, depending upon the intended use of the marker. Alternatively, rather than the lateral sides including recesses for receiving a strip of reflective tape, the lateral sides may be inclined toward the scalloped top.
While extruded roadway markers of the type described above have a number of advantages over previously developed roadway markers of the ceramic or injection molded types, previously developed extruded roadway markers of the type described in the foregoing U.S. patent applications, like many previously developed injection molded roadway markers, are bidirectional. That is, they are generally square-shaped and include two faces with a reflective medium. As a result, while such markers can be used in environments where traffic is coming from only one direction and, thus, bidirectional viewability is not required, the use of such markers in this environment is somewhat undesirable due to the costs associated with producing a bidirectional marker. These costs include more material than necessary and the expense associated with creating two reflective faces when only one is needed.
The present invention is directed toward providing lightweight, low-cost roadway markers that provide a physical rumbling cue and a visual (reflective) cue that overcome the foregoing disadvantages while retaining a constant cross-sectional shape throughout their length that allows them to be made by inexpensive extrusion manufacturing processes.